tim wrote:
On Mon, 01 Sep 2014 12:46:49 -0600, L Fisk wrote:

Need to weld a broken starter mount tab (outside hole)
on a SBC block. Hole is way beyond using a thread insert
Fairly experienced at arc welding cast with nickel rod
but also have a mig welder.
Some folks have suggested using stainless mig wire
instead of nickel arc rod.
If I just weld the hole shut the new threads will cut away most of
the weld.
Should I just vee it out completely to the outside and build up with
beads?

Is the tab broken all the way off, or is there meat all the way around
that you can weld onto?

I can't comment on stainless vs. nickel, other than to note that you
already know how to use nickel so why not stick with what you know?

I'm not sure that you're headed for happy-ville here anyway -- I would
expect that if you want something better than "hold it together long
enough to sell" you need to strip the thing down to a bare block, weld
it, then re-machine any mating surfaces that are close by (which is
presumably the bellhousing: I can't visualize a SB chevy well enough
to know if you'll be getting into the oil pan mating surface).

Is it something too rare and special for you to just get another
block?

The problem is that his weld will be hot , The thermal mass of the block
will keep the tab quite low . When the weld cools it's going to pull away
from the cast - no matter what he welds with . The only way I can see
getting around that is to weld short beads parallel to the length of the
hole and let them cool thoroughly before doing the next . And I use braxing
rod , and only fill it enough to use a permanent insert timesert ? because
the brass filler probably won't hold a thread for long .
And I can visualize that block , is it the upper or lower hole ? Lower has
a higher chance of success IMO . Hmm , almost has to be the upper , doesn't
the bolt come from the rear on the lower ?

--
Snag